Denise:  TSH is thyroid stimulating hormone, which is made in the
pituitary.  Its levels fluctuate depending on the amount of thyroid
hormone in the bloodstream.  This is called a negative feedback loop,
i.e. when the thyroid gland is underactive the pituitary releases more
TSH to stimulate increased production and vice versa.  Therefore, low TSH
levels are generally seen in hyperthyroidism and high TSH with
hypothyroidism.  However, how low or high within the normal range the TSH
level falls is probably not indicative of anything.  Also, a slight
decrease of TSH can be caused by other conditions such as depression,
even with normal thyroid function.  The only condition in which a low TSH
is associated with low levels of circulating thyroid hormone, is a rare
situation in which the pituitary itself is underactive, in which the
reason for the hypothyroidism is not a sick thyroid gland but a lack of
normal stimulation to the thyroid from TSH.
This mother's TSH is normal, so it is highly unlikely that thyroid has
anything to do with her milk supply problems.  Hope this rather
simplified version helps to clarify, not further confuse the issue.
Alicia.  [log in to unmask]